Study On The Removal Method Of Bubble In Vacuum Brazing Solder Of Compressor Blade

In the assembly of compressor blades,compared with conventional welding,vacuum brazing can obtain weldments with small deformation,compact welding structure and high overall performance under the condition of ensuring that the blades themselves will not melt,so as to ensure the overall processing quality of blade components.The solder of vacuum brazing has good fluidity and wettability.It can be used to weld devices with complex structure or micro channels to realize mass production.However,in the actual production process,due to the inevitable inclusion of bubbles in the solder,there will be welding pores that affect the quality of the welded blade components.When the diameter of the welding pores is greater than 0.4mm,the blade components will be directly scrapped.In view of the above problems,this paper carried out the following research:(1)Remove the air bubbles in the vacuum brazing filler metal by centrifugation.According to the physical parameters such as solder viscosity and density,the time needed for centrifugation is calculated according to the huge density difference between nickel powder and bubbles.Under the suitable centrifugal time,the removal of bubbles can ensure that nickel powder will not deposit.After 11 S,the 0.2mm diameter bubble floats to the upper part of the tube,which is similar to the theoretical calculation time of 10.2s.Therefore,the bubble in the solder can be removed under the effect of centrifugal force.(2)A bubble eliminator for solder was designed,and the process of bubble eliminator was simulated.Based on the principle of centrifugal force and pressure gradient force,a bubble eliminator with spiral channel is designed.CFD method is used to simulate the plane swirling structure and the whole device.In the plane swirling flow field,most of the bubbles will move to the central area along with the solder and exhaust from the gas outlet.The Eulerian Eulerian model is used to calculate the relative pressure distribution and velocity distribution,and the Eulerian Lagrangian model is used to simulate the residence time and movement distance of bubbles in the plane structure.The results show that with the increase of inlet velocity,the fluctuation coefficient of bubble residence time in the plane structure decreases,the pressure drop increases,and the degassing efficiency increases first and then decreases.(3)The degassing effect of the bubble eliminator was measured,and the porosity of the vacuum brazing sample was tested.The degassing effect was tested under different inlet speeds and different number of helices.The experimental results show that with the increase of inlet speed,degassing efficiency will increase first and then decrease.X-ray inspection and ultrasonic inspection are carried out on the welding samples,among which the effect of X-ray inspection is not ideal due to contrast and other reasons.Ultrasonic inspection can be used to measure the location of the welding pores,but it can not measure the actual size of the welding pores.The results show that the average porosity is 2.98% and 15.15% respectively,and the porosity is less than 0.4mm.